15 Common Logical Fallacies and How to Spot Them

Author: Karla Cook / Source: hubspot.com Logical fallacies -- those logical gaps that invalidate arguments -- aren't always easy to spot.

Author: Karla Cook / Source: hubspot.com

Logical fallacies — those logical gaps that invalidate arguments — aren’t always easy to spot.

While some come in the form of loud, glaring inconsistencies, others can easily fly under the radar, sneaking into everyday meetings and conversations undetected.

Having an understanding of these basic logical fallacies can help you more confidently parse the arguments and claims you participate in and witness on a daily basis — separating fact from sharply dressed fiction.

Our list is by no means an exhaustive guide to every formal and informal fallacy, but it should help you build better arguments and identify logical missteps.

15 Common Logical Fallacies

1) The Straw Man Fallacy

This fallacy occurs when your opponent over-simplifies or misrepresents your argument (i.e., setting up a “straw man”) to make it easier to attack or refute. Instead of fully addressing your actual argument, speakers relying on this fallacy present a superficially similar — but ultimately not equal — version of your real stance, helping them create the illusion of easily defeating you.

Example:

John: I think we should hire someone to redesign our website.

Lola: You’re saying we should throw our money away on external resources instead of building up our in-house design team? That’s going to hurt our company in the long run.

2) The Bandwagon Fallacy

Just because a significant population of people believe a proposition is true, doesn’t automatically make it true. Popularity alone is not enough to validate an argument, though it’s often used as a standalone justification of validity. Arguments in this style don’t take into account whether or not the population validating the argument is actually qualified to do so, or if contrary evidence exists.

While most of us expect to see bandwagon arguments in advertising (e.g., “three out of four people think X brand toothpaste cleans teeth best”), this fallacy can easily sneak it’s way into everyday meetings and conversations.

Example:

The majority of people believe advertisers should spend more money on billboards, so billboards are objectively the best form of advertisement.

3) The Appeal to Authority Fallacy

While appeals to authority are by no means always fallacious, they can quickly become dangerous when you rely too heavily on the opinion of a single person — especially if that person is attempting to validate something outside of their expertise.

Getting an authority figure to back your proposition can be a powerful addition to an existing argument, but it can’t be the pillar your entire argument rests on. Just because someone in a position of power believes something to be true, doesn’t make it true.

Despite the fact that our Q4 numbers are much lower than usual, we should push forward using the same strategy because our CEO Barbara says this is the best approach.

4) The False Dilemma Fallacy

This common fallacy misleads by presenting complex issues in terms of two inherently opposed sides. Instead of acknowledging that most (if not all) issues can be thought of on a spectrum of possibilities and stances, the false dilemma fallacy asserts that there are only two mutually exclusive outcomes.

This fallacy is particularly problematic because it can lend false credence to extreme stances, ignoring opportunities for compromise or chances to re-frame the issue in a new way.

We can either agree with Barbara’s plan, or just let the project fail. There is no other option.

5) The Hasty Generalization Fallacy

This fallacy occurs when someone draws expansive conclusions based on inadequate or insufficient evidence. In other words, they jump to conclusions about the validity of a proposition with some — but not enough — evidence to back it up, and overlook potential counterarguments.

Two members of my team have become more engaged employees after taking public speaking classes. That proves we should have mandatory public speaking classes for the whole company to improve employee engagement.